KR20020054053A - Apparatus and method for frame detecting by considering random pattern in STM - Google Patents

Abstract

The present invention provides a frame detecting apparatus and method for considering a random pattern of the synchronous transmission mode, the receiver of the synchronous transmission mode for transmitting and receiving a signal with the transmitter, the frame pattern in the random data transmitted from the transmitter The displayed position includes: a frame pattern detector for finding; A frame allocator for allocating a frame based on the frame pulse identified by the frame pattern found by the frame pattern detector; The frame allocator includes an overhead drop unit for dropping overhead from the data allocated in the frame and extracting respective values displayed in the frame, thereby providing the normal frame patterns A1 and A2 in the STM-16 overhead processor function. Even if random data having the same value occurs periodically, the frame detection function can be operated normally without being affected.

Description

Apparatus and method for frame detecting by considering random pattern in STM}

The present invention relates to an apparatus and method for detecting a frame in consideration of a random pattern in a synchronous transmission mode, and in particular, a normal frame pattern (A1, A2) in an STM-16 (Synchronous Transfer Module level 16) overhead processor function. The present invention relates to a frame detection apparatus and method for considering a random pattern of a synchronous transmission mode in which a frame detection function is not affected by a random occurrence of random data having the same value as) and is suitable for normal operation.

In general, SDH (Synchronous Digital Hierarchy) is a standard technology for synchronous data transmission on an optical medium, and is internationally equivalent to Synchronous Optical Network (SONET). Both technologies are faster and less expensive to access networks than traditional PDH (Plesiochronous Digital Hierarchy) devices.

Also in digital telephone transmission, "synchronous" means that the bits belonging to one call all move in one transmission frame. "Plesiochronous" means a call that is nearly synchronous or that one call must be extracted from one or more transmission frames.

SDH uses the STM series and speeds that follow. These include STM-1 at 155 Mbps, STM-4 at 622 Mbps, STM-16 at 2.488 Gbps, and STM-64 at 10 Gbps.

And data transmission of 2.488Gbps capacity is performed when the signal having the STM-16 frame structure of FIG. 1 is serially transmitted from the first bit in the upper left to the last bit in the lower right in serial. When such a signal is repeatedly transmitted through an optical cable, the repetition of this frame is defined as transmission of an STM-16 signal.

2 is a block diagram of a conventional transmission / reception apparatus of a synchronous transmission mode.

As shown here, the transmitter 10 includes: a frame allocation unit 11 for allocating a frame to data; An overhead insertion unit (12) for inserting an overhead into the data allocated by the frame allocation unit (11); And a frame byte generator 13 for generating and transmitting a frame byte to the data of the overhead inserter 12.

In addition, the receiver 20 includes: a frame byte detector 21 for detecting a frame byte from the transmitted STM-16 signal; A frame allocation unit (22) for allocating a frame by using the frame byte detected by the frame byte detection unit (21); The frame allocator 22 includes an overhead drop unit 23 for dropping overhead from the data allocated to the frame.

3 is a flowchart illustrating a frame detection method of a conventional synchronous transmission mode.

As shown therein, detecting the frame byte upon receiving the STM-16 signal (ST11) (ST12); Arranging each frame based on the detected frame byte and allocating a frame (ST13); Dropping overhead in the frame allocated data (ST14) is performed.

Thus, when data having a capacity of 2.488 Gbps is transmitted, the STM-16 frame data structure is shown in FIG. 1, and the portion corresponding to the payload in each frame has a different value as the portion on which the data is loaded. Overhead has a value suitable for each function.

The frame pattern bytes indicated by A1 and A2 in the overhead have a fixed value. The values are "11110110" and "00101000" in binary, respectively, A1 and A2.

Since the values of the frame bytes A1 and A2 have a fixed value every frame, they serve as a reference for finding a frame.

A1 and A2 are a total of 96 bytes, 48 bytes each, as shown in FIG.

In order for the transmission of the STM-16 grade transmission / reception to be performed normally, the transmitted portions have the values of “11110110” and “00101000” at the corresponding positions as “A1” and “A2”.

Then, the position corresponding to A1 and A2 is found in the received part, and the position of each overhead is found by using this as a reference for aligning each frame. At this time, it finds the overhead for each function and performs the function required for transmission / reception.

The process of finding the values of "11110110" and "00101000" searches for all signals sequentially input.

When the retrieved value appears continuously (250us) in one frame interval, it is called an "inframe" state.

In addition, when the values of "11110110" and "00101000" are not continuously searched for 3 ms at one frame interval, this is called "out of frame."

Therefore, in order for the transmit / receive function to work smoothly in the STM-16 overhead, the location of A1 and A2 must be found first.

In order to find the position of A1 and A2 in the received signal, since the signals are not divided by frames, all the input signals must be sequentially searched. A total of 96 bytes of A1 and A2 bytes retrieved are used as a criterion to indicate the start of each frame.

Starting from the found frame bytes A1 and A2, other overhead signals in FIG. 1 are searched as necessary. Perform each unique function at the location you find.

However, in the prior art, the position of A1 and A2 bytes is first found in order to find the starting point of each frame. As shown in FIG. 1, the portion corresponding to the payload of each frame may have a value in the frame bytes of A1 and A2. There was a problem that could be. Therefore, there was a risk that the frame byte indicating the start of one frame may occur multiple times. Accordingly, if the pattern continues to occur regardless of the interval between the frames, even if the normal frame pattern does not come in, there is a problem that only a few pattern states are recognized as an "inframe" state.

Accordingly, the present invention has been proposed to solve the above-mentioned general problems, and an object of the present invention is to periodically generate random data having the same value as the normal frame patterns A1 and A2 in the STM-16 overhead processor function. The present invention provides a frame detecting apparatus and method thereof in consideration of a random pattern in a synchronous transmission mode that can operate normally without being affected by the frame detection function.

In order to achieve the above object, a frame detection apparatus considering a random pattern of a synchronous transmission mode according to an embodiment of the present invention,

A synchronous transmission mode receiver for transmitting and receiving a signal, the receiver comprising: a frame pattern detection unit for finding a position where a frame pattern is displayed in random data transmitted from the transmitter; A frame allocator for allocating a frame based on the frame pulse identified by the frame pattern found by the frame pattern detector; The frame allocation unit includes an overhead drop unit for extracting respective values displayed in the frame by dropping the overhead from the frame allocated data.

Frame detection method considering the random pattern of the synchronous transmission mode according to an embodiment of the present invention to achieve the above object,

A receiver in a synchronous transmission mode for transmitting and receiving a signal with a transmitter, the receiver comprising: a first step of downconverting a bit rate of random data transmitted from the transmitter; Demultiplexing the down-converted random data to determine whether a frame byte is searched; A third step of determining whether a frame pattern occurs in a part of a frame when the frame byte is found; A fourth step of determining whether the frame pattern is continuous for a predetermined frame when occurring in some of the frame patterns at the same time; When the frame pattern is continuous for a predetermined frame, the technical configuration is characterized by including a fifth step of defining a frame starting point using the position of the frame pattern, and the frame reference.

1 is a view showing a typical STM-16 frame structure,

2 is a block diagram of a transmission / reception apparatus of a conventional synchronous transmission mode.

3 is a flowchart illustrating a frame detection method of a conventional synchronous transmission mode.

4 is a block diagram of a frame detection apparatus considering a random pattern of a synchronous transmission mode according to the present invention;

FIG. 5 is a detailed block diagram of the frame pattern detector of FIG. 4;

6 is a flowchart illustrating a frame detection method considering a random pattern of a synchronous transmission mode according to the present invention.

Explanation of symbols on the main parts of the drawings

10 transmitter 11 frame allocation unit

12: overhead insertion part 13; Frame byte generator

20: Receiver 21: frame byte detection unit

22: frame allocation unit 23: overhead drop unit

30: frame pattern detector 31: bit rate down converter

32: frame byte search unit 33: continuous frame search unit

34: frame pulse generator

Hereinafter, an embodiment according to the present invention, a frame detection apparatus considering a random pattern of a synchronous transmission mode, and a method thereof, will be described with reference to the accompanying drawings.

4 is a block diagram of a frame detection apparatus considering a random pattern of a synchronous transmission mode according to the present invention.

As shown in the figure, in the receiver 20 of the synchronous transmission mode that transmits and receives a signal with the transmitter 10, a position in which the frame patterns A1 and A2 are displayed in the random data transmitted from the transmitter 10 is represented. A frame pattern detector 30 for searching; A frame allocator (22) for allocating frames based on the frame pulses identified by the frame patterns found by the frame pattern detector (30); The frame allocator 22 includes an overhead drop unit 23 for dropping overhead from the data allocated in the frame and extracting respective values displayed in the frame.

The transmitter 10 further includes a frame allocator 11 for allocating a frame to data; An overhead insertion unit (12) for inserting an overhead into the data allocated by the frame allocation unit (11); And a frame byte generator 13 for generating and transmitting a frame byte to the data of the overhead inserter 12.

FIG. 5 is a detailed block diagram of the frame confirmation detecting unit in FIG. 4.

As shown therein, a bitrate downconversion section 31 for downconverting the bitrate of the transmitted random data; A frame byte search unit (32) for searching a frame byte in the random data down-converted by the bit rate down converter (31); A continuous frame search unit (33) for searching whether the frame bytes searched by the search unit (32) for the frame byte are continuously searched for a predetermined number or more; The continuous frame search unit 33 includes a frame pulse generator 34 generating frame pulses and transmitting the frame pulses to the frame allocator 22 based on whether a predetermined number of frame bytes are continuously searched.

In the above, the frame byte search unit 32 selects a part of frames to find a frame pattern.

In the above, the frame byte search unit 32 searches the bytes corresponding to the 1st, 47th, 48th, and 96th frames to find the frame pattern.

In the above, the continuous frame search unit 33 determines that normal transmission / reception is performed when a desired frame is continuously searched in a predetermined number or more frames, and when a signal in which a frame byte is not searched is transmitted continuously for a predetermined time, It is determined as "out of frame".

6 is a flowchart illustrating a frame detection method considering a random pattern of a synchronous transmission mode according to the present invention.

As shown here, a receiver 20 in a synchronous transmission mode for transmitting and receiving a signal to and from a transmitter 10, comprising: a first step (ST21) of downconverting a bit rate of transmitted random data; Demultiplexing the down-converted random data to determine whether a frame byte is searched (ST22) (ST23); A third step (ST24) of determining whether a frame pattern occurs simultaneously in a part of a frame when the frame byte is found; A fourth step (ST25) of determining whether the frame patterns A1 and A2 are continuous for a predetermined frame if they occur simultaneously in some of the frame patterns; If the frame patterns A1 and A2 are continuous for a predetermined frame, the frame start point is defined using the position of the frame pattern, and the fifth step ST26 and ST27 are used to define the frame reference.

In the third step, the first, 47th, 48th, and 96th bytes of the frame are searched to determine whether the frame pattern is generated at the same time.

The operation of the frame detection apparatus and method thereof considering the random pattern of the synchronous transmission mode according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First of all, alignment to find the position of a frame is important for smooth transmission and reception.

Therefore, the present invention is a process for finding patterns of A1 and A2, which is a reference for frame alignment, and even if patterns of “11110110” and “00101000” occur within the payload, the pattern search function finds the position of the frame accurately.

In FIG. 4, the transmitter 10 includes a frame allocator 11, an overhead inserter 12, and a frame byte generator 13.

The frame allocator 11 allocates a frame to data and determines and arranges a reference of a start position of the frame to have a frame structure as shown in FIG. 1.

The overhead inserting unit 12 inserts an overhead into the frame allocated data by the frame allocating unit 11 and performs a function of adding a value to a position indicated in the frame of FIG. 1.

The frame byte generating unit 13 generates and transmits a frame byte to the data of the overhead inserting unit 12, and adds the values "11110110" and "00101000" to the positions indicated by A1 and A2 in the frame. It performs the function.

In addition, the receiver 10 includes a frame pattern detector 30, a frame allocator 22, and an overhead drop unit 23.

The frame pattern detection unit 30 finds a position marked with the frame patterns A1 and A2 in the transmitted random data, and finds a position marked A1 and A2 in the random data.

The frame allocator 22 allocates frames based on the frame pulses identified by the frame patterns found by the frame pattern detector 30, which is as shown in FIG. 1 based on the frame pulses found by finding values of A1 and A2. Perform the function of sorting the structure.

The overhead drop unit 23 extracts the respective values displayed in the frame by dropping the overhead from the frame allocated data in the frame allocation unit 22. The overhead drop unit 23 extracts the respective values displayed in the frame of FIG. Extract.

Meanwhile, a continuous signal of 2.488 Gbps capacity having a frame structure as shown in FIG. 1 is transmitted and received through an optical fiber. The portion corresponding to the overhead of the frame as shown in Figure 1 has a unique function for smooth transmission and reception. The payload portion corresponds to data on the transmission / reception, and the pattern is not constant and has a random value.

For normal transmission and reception, the exact position of one frame configured as shown in FIG. 1 must be found.

Since the bit rate of the transmitted / received signal is 2.488 Gbps, it is practically impossible to find the values of A1 and A2 as physical devices. Find the location of A2.

Since A1 and A2 are 48 bytes each, a total of 96 bytes, in order to find the positions of A1 and A2, all 96 bytes must be latched and shifted by one bit to find the positions of A1 and A2. However, in order to latch all 96 bytes, one flip-flop is required to latch one bit, so a total of 96x8 = 768 flip-flops are required, resulting in a circuit size of 768 flip-flops.

The circuit is too big to use so many flip-flops, so we select some of the 96 bytes to find the patterns of A1 and A2.

At this time, the bytes corresponding to some are bytes corresponding to the 1st, 47th, 48th, and 96th when all 96 bytes of A1 and A2 are sequentially listed in FIG. 1. These values are "11110110", "11110110", "00101000", and "00101000" in order.

Since the same pattern as the pattern of these four bytes may occur on the payload, it is necessary to determine whether the retrieved pattern is within the overhead.

The determination starts from the pattern of the first four bytes retrieved, and searches whether the same pattern of four bytes is found in the portion corresponding to one frame interval. At this time, the pattern of four bytes "11110110", "11110110", "00101000", and "00101000" generated before one frame interval is ignored.

When a desired pattern is searched continuously in two frames at one frame interval, it can be said that normal transmission / reception is achieved. This is called an inframe state.

If it is determined that normal transmission and reception are performed, that is, if the pattern of frame bytes A1 and A2 is searched for two consecutive frames, when the signal for which the frame byte is not searched is transmitted for 3 ms consecutively, it is called out of frame. do. In the out-of-frame state, it is judged whether it is normally transmitted / received by judging whether it is searched continuously for two frames based on the pattern of “11110110”, “11110110”, “00101000”, and “00101000” which are first searched again. To determine whether it is in-frame.

As described above, according to the present invention, even if random data having the same value as the normal frame patterns A1 and A2 is periodically generated in the STM-16 overhead processor function, the frame detection function is normally not affected.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, in the frame detection apparatus and method considering the random pattern of the synchronous transmission mode according to the present invention, in the STM-16 overhead processor function, random data having the same value as the normal frame patterns A1 and A2 is obtained. Even if it occurs periodically, the frame detection function is not affected and there is an effect that can operate normally.

In addition, the present invention also has the effect of preventing the wrong in-frame state caused by the pattern generation of "11110110", "00101000" on the payload other than the frame byte on the transmission / reception.

Claims (7)

In the receiver of the synchronous transmission mode for transmitting and receiving a signal with the transmitter, A frame pattern detection unit for finding a position where the frame pattern is displayed in the random data transmitted from the transmitter; A frame allocator for allocating a frame based on the frame pulse identified by the frame pattern found by the frame pattern detector; And an overhead drop unit for extracting respective values displayed in the frame by dropping the overhead from the data allocated in the frame by the frame allocator. The method of claim 1, wherein the frame confirmation detection unit, A bitrate downconversion unit for downconverting the bitrate of the transmitted random data; A frame byte search unit searching for a frame byte in the random data down-converted by the bit rate down-conversion unit; A continuous frame search unit for searching whether the frame bytes searched by the search unit in the frame bytes are continuously searched for a predetermined number or more; A frame pulse generator configured to generate a frame pulse and transmit the frame pulse to the frame allocator according to whether the frame bytes are continuously searched for a predetermined number or more by the continuous frame search unit. Device. The method of claim 2, wherein the frame byte search unit, A frame detection apparatus in consideration of a random pattern of the synchronous transmission mode, characterized in that selecting a part of the frame to find a frame pattern. The method of claim 2, wherein the frame byte search unit, A frame detection apparatus considering a random pattern of a synchronous transmission mode, characterized by searching for bytes corresponding to the first, 47th, 48th, and 96th frames. The method of claim 2, wherein the continuous frame search unit, If a desired frame is searched continuously in a predetermined number of frames or more, it is determined that normal transmission / reception is performed. Frame detection apparatus considering the random pattern of the synchronous transmission mode. In the receiver of the synchronous transmission mode for transmitting and receiving a signal with the transmitter, Downconverting the bitrate of random data transmitted from the transmitter; Demultiplexing the down-converted random data to determine whether a frame byte is searched; A third step of determining whether a frame pattern occurs in a part of a frame when the frame byte is found; A fourth step of determining whether the frame pattern is continuous for a predetermined frame when occurring in some of the frame patterns at the same time; If the frame pattern is continuous for a predetermined frame, a frame in consideration of the random pattern of the synchronous transmission mode, characterized in that the step of defining a frame starting point using the position of the frame pattern, and defining the frame reference Detection method. The method of claim 6, wherein the third step, A method of detecting a frame in consideration of a random pattern in a synchronous transmission mode, characterized by determining whether a frame pattern occurs simultaneously by searching for bytes corresponding to the first, 47th, 48th, and 96th of a frame.